Merge pull request #66971 from tnozicka/informer-watcher

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

#50102 Task 2: Add UntilWithSync

**What this PR does / why we need it**:
This is a split off from https://github.com/kubernetes/kubernetes/pull/50102 to go in smaller pieces.

Introduces UntilWithSync based on informer.

**Needs https://github.com/kubernetes/kubernetes/pull/66906 first**
/hold

**Release note**:
```release-note
NONE
```

/priority important-soon
/kind bug
(bug after the main PR which is this split from)

Kubernetes-commit: c4f355a2ad9692f5459541d4e4d94fcbc5f7d946

vendor/k8s.io/apimachinery/pkg/watch/watch.go

@@ -268,3 +268,50 @@ func (f *RaceFreeFakeWatcher) Action(action EventType, obj runtime.Object) {
 		}
 	}
 }
+
+// ProxyWatcher lets you wrap your channel in watch Interface. Threadsafe.
+type ProxyWatcher struct {
+	result chan Event
+	stopCh chan struct{}
+
+	mutex   sync.Mutex
+	stopped bool
+}
+
+var _ Interface = &ProxyWatcher{}
+
+// NewProxyWatcher creates new ProxyWatcher by wrapping a channel
+func NewProxyWatcher(ch chan Event) *ProxyWatcher {
+	return &ProxyWatcher{
+		result:  ch,
+		stopCh:  make(chan struct{}),
+		stopped: false,
+	}
+}
+
+// Stop implements Interface
+func (pw *ProxyWatcher) Stop() {
+	pw.mutex.Lock()
+	defer pw.mutex.Unlock()
+	if !pw.stopped {
+		pw.stopped = true
+		close(pw.stopCh)
+	}
+}
+
+// Stopping returns true if Stop() has been called
+func (pw *ProxyWatcher) Stopping() bool {
+	pw.mutex.Lock()
+	defer pw.mutex.Unlock()
+	return pw.stopped
+}
+
+// ResultChan implements Interface
+func (pw *ProxyWatcher) ResultChan() <-chan Event {
+	return pw.result
+}
+
+// StopChan returns stop channel
+func (pw *ProxyWatcher) StopChan() <-chan struct{} {
+	return pw.stopCh
+}